Fuel pump

ABSTRACT

Fuel pump ( 10 ) may comprise a casing ( 18 ) and a substantially disc-shaped impeller ( 20 ) rotating within the casing. A plurality of groups of concavities ( 20   a   , 20   b ), arranged in concentric circles with respect to the rotational axis of the impeller, may be formed in at least one surface of the impeller. A plurality of grooves ( 24   a   , 24   b   , 24   c ) may be formed in the inner surface of the casing that faces the surface in which the groups of concavities are formed. Each groove extends from an upstream end to a downstream end. Fuel is drawn in from the outside of the casing to the upstream ends of each of the grooves ( 24   a   , 24   b   , 24   c ), and the fuel drawn into the casing is discharged to the outside of the casing from the downstream ends of each of the grooves ( 24   a   , 24   b   , 24   c ). Each of the plurality of grooves ( 24   a   , 24   b   , 24   c ) may face at least two or more of the plurality of groups of concavities ( 20   a   , 20   b ) formed in the impeller.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2005-240367, filed on Aug. 22, 2005, the contents of which are hereby incorporated by reference into the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel pump for drawing in fuel (e.g., gasoline), increasing the pressure thereof, and discharging the pressurized fuel.

2. Description of the Related Art

A fuel pump is employed in order to supply fuel in a fuel tank to an internal combustion engine. This fuel pump normally comprises a substantially disc-shaped impeller. The impeller is rotatably housed inside a casing. A group of concavities is formed in the surface of the impeller, and a groove that extends from the upstream end to the downstream end is formed in the inner surface of the casing in an area opposite the group of concavities of the impeller. The upstream end of the groove is linked with the outside of the casing by a intake hole, and the downstream end of the groove is linked with the outside of the casing by a discharge hole.

With this fuel pump, fuel is drawn into the casing from the intake hole when the impeller rotates. The fuel drawn into the casing flows from the intake hole along the groove toward the discharge hole. The fuel is pressurized as it flows inside the groove from the upstream end to the downstream end thereof, and the pressurized fuel is discharged to the outside of the casing from the discharge hole.

With this fuel pump, a pump passage is formed by the groove of the casing and the group of concavities of the impeller, and the fuel will be pressurized by flowing through the pump passage. Thus, when a plurality of pump passages can be provided, the pumping capacity of the fuel pump can be increased. Accordingly, fuel pumps have been developed in which two groups of concavities are formed in concentric circles in the impeller, two grooves that face each group of concavities are formed in the inner surface of the casing, and the corresponding groups of concavities and grooves independently form 2 pump passages (e.g., Japanese Laid-open Utility Model Publication No. 62-66292).

BRIEF SUMMARY OF THE INVENTION

In the fuel pump described above, a plurality of independent pump passages are formed therein by providing a plurality of groups of concavities and a plurality of grooves, thereby increasing the pumping capacity thereof. However, with this fuel pump, there are disparities between the length of the pump passage on the inner side (the group of concavities and the groove formed on the inner side) and the length of the pump passage on the outer side (the group of concavities and the groove formed on the outer side) (in other words, the pump passage on the inner side is short, and the pump passage on the outer side is long), and thus the degree to which the fuel in each pump passage is pressurized will differ. Because of this, a problem has occurred in which the fuel pressure applied to the inner side and the outer side of the impeller will diverge, and thereby cause the impeller to tilt and produce wear.

It is an object of the present teachings to provide a fuel pump, which comprises a plurality of pump passages formed by forming a plurality of groups of concavities in the impeller, and forming a plurality of grooves in the inner surface of the casing, that can inhibit the tilting of the impeller.

In one aspect of the present teachings, a fuel pump may comprise a casing and a substantially disc-shaped impeller rotating within the casing. A plurality of groups of concavities, arranged in concentric circles with respect to the rotational axis of the impeller, may be formed in at least one surface of the impeller. A plurality of grooves may be formed in the inner surface of the casing that faces the surface in which the groups of concavities are formed. Each groove extends from an upstream end to a downstream end. An intake hole and discharge hole may be formed in the casing, the intake hole passing from the exterior of the casing to the upstream end of each groove, and the discharge hole passing from the exterior of the casing to the downstream end of each groove. Each of the plurality of grooves may comprise at least a first groove portion that faces one of the plurality of groups of concavities, a second groove portion that faces a group of concavities that is different from the group of concavities facing the first groove portion, and a third groove portion that links the first groove portion and the second groove portion.

With this fuel pump, a portion of the grooves of the casing will face one of the groups of concavities of the impeller, and another portion of the grooves will face the other groups of concavities of the impeller. Thus, a pump passage formed by means of a group of concavities in the impeller and a groove in the inner surface of the casing will be formed across at least two of the plurality of groups of concavities in the impeller. Because of this, each groove can have a portion that faces a group of concavities on an inner circumferential side and a portion that faces a group of concavities on an outer circumferential side, and thus the difference in the length of each groove (i.e., the pump passage) can be reduced. Therefore, the differences in the fuel pressure of the fuel pressurized in each pump passage can be reduced, and the tilting of the impeller can be inhibited.

In the fuel pump described above, it is preferable that the length from the upstream end to the downstream end of each groove be substantially equal. According to this configuration, the fuel pressure of the fuel pressurized in each pump passage can be substantially equalized, and the tilting of the impeller can be inhibited effectively.

In addition, it is preferable that the upstream end of each groove be arranged in symmetrical positions with respect to the rotational axis of the impeller, and preferable that the downstream end of each groove be arranged in symmetrical positions with respect to the rotational axis of the impeller. According to this configuration, the balance of the fuel pressure applied to the impeller can be improved, and the tilting of the impeller can be inhibited effectively.

These aspects and features may be utilized singularly or, in combination, in order to make improved fuel pump. In addition, other objects, features and advantages of the present teachings will be readily understood after reading the following detailed description together with the accompanying drawings and claims. Of course, the additional features and aspects disclosed herein also may be utilized singularly or, in combination with the above-described aspect and features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a fuel pump according to a representative embodiment of the present teachings.

FIG. 2 is a plan view of a pump cover when viewed from the impeller side.

FIG. 3 is a plan view of an impeller.

FIG. 4 is a plan view of a pump cover according to another representative embodiment when viewed from the impeller side.

DETAILED DESCRIPTION OF THE INVENTION

A fuel pump 10 according to a representative embodiment of the present teachings will be described with reference to the drawings. The fuel pump 10 may be used in an automobile, the fuel pump 10 being utilized within a fuel tank and being utilized for supplying fuel to an engine of the automobile. As shown in FIG. 1, the fuel pump 10 comprises a motor portion 70 and a pump portion 12.

The motor portion 70 comprises a housing 72, a motor cover 73, magnets 74, 75, and a rotor 76. The housing 72 is formed in a substantially cylindrical shape. The motor cover 73 is attached to the housing 72 by caulking the upper end 72 a of the housing 72. A discharge port 73 a is formed in the motor cover 73. The magnets 74, 75 are fixed to the inner walls of the housing 72. The rotor 76 has a main body 77, and a shaft 78 that vertically extends through the main body 77. The main body 77 comprises a core 79 that is fixed to the shaft 78, a coil (not shown in the drawings) that is wound around the core 79, and a resin part 80 that fills in around the coil. A commutator 84 is arranged on the upper end of the main body 77. A brush 90 is in contact with the upper end surface of the commutator 84. The brush 90 is urged downward by a spring 92 which is fastened on one end to the motor cover 73. When the brush 90 abrades, the brush 90 will move downward in response to the abrasion, and the brush 90 and the commutator 84 will thereby remain in contact with each other. The upper end 78 a of the shaft 78 is rotatably mounted on the motor cover 73 via a bearing 81. The lower end 78 b of the shaft 78 is rotatably mounted on a pump cover 14 of the pump portion 12 via a bearing 82.

The pump portion 12 comprises a casing 18 and a substantially disc-shaped impeller 20. As shown in FIG. 3, a first group of concavities 20 a is formed in the outer circumferential portion of the impeller 20. The first group of concavities 20 a is separated from the outer circumferential surface 20 f of the impeller 20 by an outer circumferential wall 20 d of the impeller 20.

A second group of concavities 20 b is formed inward, from the position in which the first group of concavities 20 a of the impeller 20 is formed. The second group of concavities 20 b is separated from the first group of concavities 20 a by a surface 20 c of the impeller 20.

As is clear from FIG. 3, the first group of concavities 20 a and the second group of concavities 20 b are arranged in concentric circles with respect to the rotational axis of the impeller 20. Each concavity of the first group of concavities 20 a is arranged so as to be equally spaced in the circumferential direction of the impeller 20. Likewise, each concavity of the second group of concavities 20 b is arranged so as to be equally spaced in the circumferential direction of the impeller 20, and so that the position of each concavities of the first group of concavities 20 a corresponds thereto. Because of this, the number of concavities in the first group of concavities 20 a is equal to the number of concavities in the second group of concavities 20 b. In addition, because the first group of concavities 20 a is formed outward from the second group of concavities 20 b, the concavities of the first group of concavities 20 a will be larger in the circumferential direction than the concavities of the second group of concavities 20 b. However, the concavities of the first group of concavities 20 a and the concavities of the second group of concavities 20 b will have the same size (i.e., length) in the radial direction of the impeller 20.

Note that as shown in FIG. 1, a first group of concavities 21 a and a second group of concavities 21 b are formed in the lower surface of the impeller 20, and are identical to those in the upper surface of the impeller 20. The first group of concavities 21 a and the second group of concavities 21 b are constructed in the same way as the first group of concavities 20 a and the second group of concavities 20 b described above. Base portions of each of the first groups of concavities 20 a, 21 a communicate via through-hole (not shown in the drawings), and base portions of each of second groups of concavities 20 b, 21 b also communicate via a through-hole. In addition, a fitting hole 20 e is formed in the center of the impeller 20, and extends therethrough in the thickness direction.

The casing 18 comprises the pump cover 14 and a pump body 16. As shown in FIGS. 1 and 2, a recess 14 a is formed in the surface of the impeller side of the pump cover 14 (i.e., the lower surface). The diameter of the recess 14 a is approximately the same as the diameter of the impeller 20. The recess 14 a has approximately the same depth as the thickness of the impeller 20. The impeller 20 is rotatably inserted into the recess 14 a.

The casing 18 with the impeller 20 installed in the recess 14 a of the pump cover 14 is fixed to the housing 72 by caulking the lower end 72 b of the housing 72. The lower end 78 b of the shaft 78 is press fitted into the fitting hole 20 e of the impeller 20, with the portion thereof that is further downward from the portion supported by the bearing 82. Because of this, the impeller 20 will rotate when the rotor 76 rotates. A thrust bearing 33 that receives the thrust load of the rotor 76 is interposed between the lower end of the shaft 78 and the pump body 16.

As shown in FIG. 2, three grooves 24 a, 24 b, 24 c are formed in the bottom surface of the recess 14 a of the pump cover 14 (hereinafter referred to as the “lower surface of the pump cover”).

The groove 24 a comprises a first groove portion 28 a that extends in an area facing the second group of concavities 20 b in the upper surface of the impeller 20, a second groove portion 28 c that extends in an area facing the first group of concavities 20 a in the upper surface of the impeller 20, and a third groove portion 28 b that connects the downstream end of the first groove portion 28 a and the upstream end of the second groove portion 28 c. The upstream end 27 a of the first groove portion 28 a is the upstream end of the groove 24 a, and the downstream end 29 a of the second groove portion 28 c is the downstream end of the groove 24 a.

As shown in FIGS. 1 and 2, the upstream end 27 a of the groove 24 a is linked to an intake hole 32 a. The intake hole 32 a extends from the groove 24 a to the lateral surface of the pump cover 14. The intake port of the fuel intake hole 32 a (i.e., the end portion opposite the groove 24 a side) is open to the exterior via an opening formed in the housing 72. Thus, the groove 24 a is linked to the outside of the fuel pump 10 via the intake hole 32 a.

In contrast, the downstream end 29 a of the groove 24 a is linked to a discharge hole 26 a. The discharge hole 26 a extends from the groove 24 a to the upper surface of the pump cover 14. The discharge hole 26 a links the groove 24 a and the outside of the casing 18. The discharge hole 26 a opens on the upper surface of the pump cover 14.

As is clear from FIG. 2, the grooves 24 b and 24 c are constructed in the same way as the groove 24 a, and have the same passage length as the groove 24 a. The intake hole 32 a is connected to the upstream end 27 b of the groove 24 b, and the discharge hole 26 a is connected to the downstream end 29 b of the groove 24 b. Likewise, the intake hole 32 a is connected to the upstream end 27 c of the groove 24 c, and the discharge hole 26 a is connected to the downstream end 29 c of the groove 24 c. By respectively connecting the upstream ends 27 a, 27 b, 27 c of the grooves 24 a, 24 b, 24 c to the intake hole 32 a, and respectively connecting the downstream ends 29 a, 29 b, 29 c of the grooves 24 a, 24 b, 24 c to the discharge hole 26 a, the grooves 24 a, 24 b, 24 c form independent fuel passages.

Note that a slight gap is formed between the outer circumferential surface 20 f of the impeller 20 and the lateral surface of the recess 14 a of the pump cover 14. This gap is provided so that the impeller 20 will rotate smoothly.

Like the grooves 24 a, 24 b, 24 c formed in the pump cover 14, three grooves 30 a, 30 b, 30 c are formed in the surface of the pump body 16 on the impeller 20 side (i.e., the upper surface of FIG. 1) (however, reference numeral 30 is shown in FIG. 1).

The grooves 30 a, 30 b, 30 c respectively comprises a first groove portion that extends in an area facing the second group of concavities 21 b in the lower surface of the impeller 20, a second groove portion that extends in an area facing the first group of concavities 21 a in the lower surface of the impeller 20, and a third groove portion that connects the downstream end of the first groove portion and the upstream end of the second groove portion. In each groove 30 a, 30 b, 30 c, the upstream end of the first groove portion is the upstream end of that groove, and the downstream end of the second groove portion is the downstream end of that groove. A fuel intake hole 32 b formed in the pump body 16 is linked to the upstream end of each groove 30 a, 30 b, 30 c. A discharge hole 26 b formed in the casing 18 is linked to the downstream end of each groove 30 a, 30 b, 30 c. The grooves 30 a, 30 b, 30 c also form independent fuel passages.

Note that the upstream end of the groove 30 a and the upstream end 27 a of the groove 24 a are arranged in symmetrical positions, and the downstream end of the groove 30 a and the downstream end 29 a of the groove 24 a are also arranged in symmetrical positions. Likewise, the groove 30 b and the groove 24 b, and the groove 30 c and the groove 24 c, are also adjusted to the targeted positional relationship.

When the impeller 20 rotates, swirl flow is generated between the concavities 21 a, 21 b in the lower side of the impeller 20 and each groove 30 a, 30 b, 30 c of the pump body 16. In other words, swirl flow is created in the concavities 21 a, 21 b and each groove 30 a, 30 b, 30 c when the fuel in the concavities 21 a, 21 b and the groove 30 a, 30 b, 30 c flows to the inward sides of the concavities 21 a, 21 b from the grooves 30 a, 30 b, 30 c, flows then along the concavities 21 a, 21 b from the inward sides to the outward sides through the concavities 21 a, 21 b, and then returns from the outward side of the concavities 21 a, 21 b to the grooves 30 a,30 b,30 c. The fuel is pressurized along the grooves 30 a, 30 b, 30 c while being revolving as described above. Upon being pressurized along the grooves 30 a, 30 b, 30 c, the fuel is drawn in through the intake hole 32 b. The fuel pressurized in the grooves 30 a, 30 b, 30 c is fed from the discharge hole 26 b into the housing 72 of the motor portion 70. The fuel fed into the housing 72 then flows upward through the housing 72, and is discharged from the discharge port 73 a of the motor cover 73.

In addition, swirl flow is also generated between the concavities 20 a, 20 b in the upper side of the impeller 20 and each groove 24 a, 24 b, 24 c of the pump cover 14. In other words, swirl flow is created in the concavities 20 a, 20 b and the grooves 24 a, 24 b, 24 c when the fuel in the concavities 20 a, 20 b and each groove 24 a, 24 b, 24 c flows to the inward sides of the concavities 20 a, 20 b from the grooves 24 a, 24 b, 24 c, flows then along the concavities 20 a, 20 b from the inward sides to the outward sides through the concavities 20 a, 20 b, and then returns to the grooves 24 a, 24 b, 24 c from the outward sides of the concavities 20 a, 20 b. The fuel is pressurized along the grooves 24 a, 24 b, 24 c while being revolving as described above. Upon being pressurized along the grooves 24 a, 24 b, 24 c, the fuel is drawn in through the intake hole 32 b. The fuel pressurized in the grooves 24 a, 24 b, 24 c is fed from the discharge hole 26 b into the housing 72 of the motor portion 70. The fuel fed into the housing 72 then flows upward through the housing 72, and is discharged from the discharge port 73 a of the motor cover 73.

As is clear from FIG. 2, the upstream ends 27 a, 27 b, 27 c of each groove 24 a, 24 b, 24 c formed in the inner surface of the pump cover 14 are arranged in positions that are symmetrical with respect to the rotational axis of the impeller 20. In other words, the upstream ends 27 a, 27 b, 27 c of each groove 24 a, 24 b, 24 c are equidistant from the rotational axis of the impeller 20, and equally spaced in the circumferential direction of the impeller 20 (120 degrees). In addition, the downstream ends 29 a, 29 b, 29 c of each groove 24 a, 24 b, 24 c formed in the inner surface of the pump cover 14 are also arranged in positions that are symmetrical with respect to the rotational axis of the impeller 20. In other words, the downstream ends 29 a, 29 b, 29 c of each groove 24 a, 24 b, 24 c are equidistant from the rotational axis of the impeller 20, and equally spaced in the circumferential direction of the impeller (120 degrees).

The passage length of each groove 24 a, 24 b, 24 c is equal, the fuel pressure at the upstream end 27 a, 27 b, 27 c of each groove 24 a, 24 b, 24 c is substantially equal, and the fuel pressure at the downstream end 29 a, 29 b, 29 c of each groove 24 a, 24 b, 24 c is substantially equal. Because of this, the fuel pressure will be applied substantially equally to the entire upper surface of the impeller 20. In particular, by arranging the upstream ends 27 a, 27 b, 27 c and the downstream ends 29 a, 29 b, 29 c of each groove 24 a, 24 b, 24 c at equal intervals in the circumferential direction, the impeller 20 will be placed in substantially the same state as one in which the impeller 20 is supported at three points, and the impeller 20 will be effectively prevented from tilting.

In addition, because each groove 30 a, 30 b, 30 c of the pump body 16 is constructed in the same way as each groove 24 a, 24 b, 24 c of the pump cover 14, fuel pressure will be applied substantially equally to the entire lower surface of the impeller 20. In this way, the impeller 20 will be prevented from tilting.

As is clear from the above description, in the fuel pump 10 of the representative embodiment, by forming the two groups of concavities 20 a, 20 b in the upper surface of the impeller 20, and forming the grooves 24 a, 24 b, 24 c in the inner surface of the casing 18 facing the upper surface of the impeller 20, three independent pump passages are provided. In addition, by forming the two groups of concavities 21 a, 21 b in the lower surface of the impeller 20, and forming the grooves 30 a, 30 b, 30 c in the inner surface of the casing 18 facing the lower surface of the impeller 20, three independent pump passages are provided. By providing a plurality of independent pump passages, the pump capacity of the fuel pump 10 can be increased, and the pump efficiency can be improved.

In addition, even if a plurality of pump passages (grooves 24 a, 24 b, 24 c, 30 a, 30 b, 30 c) are provided, the passage lengths thereof are the same because the pump passages span both of the two groups of concavities 20 a, 20 b (or 21 a, 21 b) of the impeller 20. In this way, the fuel pressure of the fuel that flows in each pump passage will be applied substantially equally to the entire surface of the impeller 20, and thus the impeller 20 will be prevented from tilting. Because of this, uneven wear of the impeller 20 will be inhibited. In addition, the pump efficiency can also be improved by reducing the rotational resistance of the impeller 20.

Note that in the embodiment described above, three pump passages were provided in both the upper and lower surfaces of the impeller 20 by forming three grooves 24 a, 24 b, 24 c (or 30 a, 30 b, 30 c) in an inner surface of the casing facing the impeller 20. However, the present teachings are not limited to this configuration, and the number of pump passages formed in an inner surface of the casing is not limited to three. For example, as shown in FIG. 4, two grooves 124, 126 may be formed in an inner surface of the casing. Each groove 124, 126 partially faces the first group of concavities 20 a and the second group of concavities 20 b formed in the impeller 20. The upstream end 124 a of the groove 124 and the upstream end 126 a of the groove 126 are linked to the intake hole, and the downstream end 124 b of the groove 124 and the downstream end 126 b of the groove 126 are linked to the discharge hole.

Even with this embodiment, the passage length of the groove 124 and the groove 126 will be equal, and the fuel in the pump passages will be equally pressurized. In addition, the upstream ends 124 a, 126 a and the downstream ends 124 b, 126 b of the grooves 124, 126 are symmetrical with respect to the rotational axis of the impeller 20. Because of these, the fuel pressure of the fuel that flows in the groove 124 and the groove 126 will be applied substantially equally to the entire surface of the impeller 20, and thus the impeller 20 will be prevented from tilting.

In addition, in the embodiment described above, pump passages are formed in the upper and lower surfaces of the impeller, but the present teachings are not limited to this example, and the pump passages may be formed in only one of the surfaces of the impeller.

In addition, in the embodiment described above, the pump passages formed in the upper and lower surfaces of the impeller are respectively connected to the intake hole and the discharge hole, but the present teachings are not limited to this configuration, and the intake hole may be connected to only one of the surfaces of the impeller, and the discharge hole may be connected to only the other surface of the impeller.

Furthermore, in the embodiment described above, two groups of concavities were formed in the impeller, but the number of groups of concavities formed in the impeller is not limited to two, and for example, three groups of concavities may be formed in the impeller.

Furthermore, the technology of the present teachings can be applied to various types of fuel pumps other than the type of fuel pump described in the embodiment described above, e.g., the present teachings can be applied to an axial type of fuel pump.

Finally, although the preferred embodiments have been described in detail, the present embodiments are for illustrative purpose only and not restrictive. It is to be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims. In addition, the additional features and aspects disclosed herein also may be utilized singularly or in combination with the above aspects and features. 

1. A fuel pump comprising a casing and a substantially disc-shaped impeller rotating within the casing, wherein a plurality of groups of concavities arranged in concentric circles with respect to the rotational axis of the impeller are formed in at least one surface of the impeller, a plurality of grooves are formed in the inner surface of the casing that faces the surface in which the groups of concavities are formed, each groove extending from an upstream end to a downstream end, a intake hole and discharge hole are formed in the casing, the intake hole passing from the exterior of the casing to the upstream end of each groove, and the discharge hole passing from the exterior of the casing to the downstream end of each groove, and each of the plurality of grooves comprises at least a first groove portion that faces one of the plurality of groups of concavities, a second groove portion that faces a group of concavities that is different from the group of concavities facing the first groove portion, and a third groove portion that links the first groove portion and the second groove portion.
 2. A fuel pump according to claim 1, wherein the length from the upstream end to the downstream end of each groove is substantially equal.
 3. A fuel pump according to claim 2, wherein the upstream end of each groove is arranged in a symmetrical position with respect to the rotational axis of the impeller, and the downstream end of each groove is arranged in a symmetrical position with respect to the rotational axis of the impeller.
 4. A fuel pump comprising a casing and a substantially disc-shaped impeller rotating within the casing, wherein a plurality of groups of concavities arranged in concentric circles with respect to the rotational axis of the impeller are formed in at least one surface of the impeller, a plurality of grooves are formed in the inner surface of the casing that faces the surface in which the groups of concavities are formed, each groove extending from an upstream end to a downstream end, and each of the plurality of grooves formed in the inner surface of the casing face at least two or more of the plurality of groups of concavities formed in the impeller. 